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Author Topic: How electrostatic field works with laser beam?  (Read 4072 times)

Offline agnieshka

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How electrostatic field works with laser beam?
« on: 29/12/2015 13:28:55 »

Does anyone know how to effect a strong electrostatic field on a laser beam?

Thank you
« Last Edit: 12/07/2016 10:28:55 by agnieshka »


 

Offline RD

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The strangest thing is what I get: ... Centrally it is burned longitudinal line, with bars on the right and left of center  ...

The parallel tracks (of differing thickness) could be a diffraction-effect ...


http://micro.magnet.fsu.edu/primer/java/diffraction/basicdiffraction/
« Last Edit: 29/12/2015 15:25:02 by RD »
 

Offline RD

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I've got one question: If this is the effect of the diffraction, what is an obstacle or a slit to make this?

The aperture of the laser will cause a concentric diffraction pattern ...
https://en.wikipedia.org/wiki/Airy_disk

... high-power laser (UV) ... Metals ... electrical conductivity ...
Shining high-intensity UV light on metal will create the photoelectric-effect , which will effect conductivity.

Apparently you're an amateur experimenter using a high-powered-laser which is invisible to human eye.  I hope you like Labrador dogs.
« Last Edit: 29/12/2015 15:25:37 by RD »
 

Offline RD

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...  this effect does not appear when im using only two components: infrasound wave + laser or an electrostatic field + laser. All three elements must work to effect was observable ...

If you're using a laser in an electric field, then the only other phenomenon which comes to mind is the Stark effect : your laser may no longer be monochromatic if the electric field is very strong.
 

Offline evan_au

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Quote from: agnieshka
Centrally it is burned longitudinal line, with bars on the right and left of center (as shown below)
I was wondering what sort of laser it is?
Perhaps the strong acoustic pressure changes are moving the mirrors, and switching it between different modes, with different beam angles?

Quote
Metals - for the frequency of 8-9 Hz lose their electrical conductivity (COMPLETELY...)
A good test of this is the Meissner effect, usually seen only in superconducting materials.
According to the graph, you should see this for some range of acoustic frequencies.
See: http://en.wikipedia.org/wiki/Meissner_effect
 
 

Offline Atomic-S

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To what is the acoustic wave applied? The laser itself? The target? The air in between?  Likewise, to what is the high voltage applied?
 

Offline agnieshka

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To what is the acoustic wave applied? The laser itself? The target? The air in between?  Likewise, to what is the high voltage applied?

I will try to explain everything on a simplified schematic of the device.
« Last Edit: 12/07/2016 10:30:59 by agnieshka »
 

Offline RD

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...  An acoustic wave with a frequency around 28-30 [Hz] has put a beam in vibrations. This effect was hardly noticeable, so was necessary to use a magnifying glass.  By reducing the frequency of the acoustic wave, the effect was stronger. At the frequency approx. 8-15Hz  effect was the strongest -> Beam strongly vibrated.

That sounds like a mechanical-resonance effect : the lower frequency is closer to the resonant-frequency of your apparatus & the table it's on.

... we can watch a discharge from the torus to the laser beam ...

That suggests to me the laser is ionising the something in the air.
If so that's a helluva powerful laser you've got there : please be careful.
« Last Edit: 31/12/2015 18:13:32 by RD »
 

Offline RD

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... so λ is changed ...

Not necessarily : your powerful laser combined with strong electric-field could create a purple-plasma which is intimate to the laser beam.
So the laser λ is actually unchanged , it's just the beam is surround by a purple plasma.

Unfortunately, I can not check it for λ < 435 using a diffraction grating because it is burned.

Personally I would not be in the same room with a laser-beam capable of burning anything while it was on. Web-cameras are cheap , eyesight is irreplaceable.
« Last Edit: 31/12/2015 18:49:31 by RD »
 

Offline evan_au

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Some details that I now understand from the drawing is that there is a high-voltage Tesla coil, with:
  • a high-power laser passing down the center of the coil
  • an audio amplifier driving another coil around the outside of the Tesla coil.
A Tesla coil is capable of generating quite high voltages, with corona discharge around the torus at the top.
  • Normally you would not put any conductive material near it, as the Tesla coil will arc over to the conductive material.
  • The conductive material may also change the resonant frequency of the Tesla coil; the capacitance of a Tesla coil has to be "tuned" to adjust the resonant frequency of the primary and secondary coils, to give the highest output voltage.
  • A UV laser will tend to ionize the air, forming a conductive path that short-circuits the Tesla coil. This is supported by seeing sparks from the torus to the laser beam.
  • Wrapping a coil from an audio amplifier around the Tesla coil would tend to change it's capacitance, but invites arc-over from the Tesla coil into the audio amplifier, which could easily destroy the audio amplifier.
  • Not shown here is the method for measuring the resistivity of the test material. But it looks like the high-voltage of the Tesla coil will be coupled by the ionized laser beam path into whatever device is measuring resistance.
  • Devices that measure resistance typically generate their own DC current & voltage, and don't expect to be zapped by a high-frequency, high-voltage leakage from a Tesla coil!
I suggest that either:
1. some of the voltage from the Tesla coil is finding its way into the resistance measurement, causing the appearance of zero resistance. or:
2. The laser is ionizing the surface of the material, and turning it into a plasma. A plasma has very low resistance, but it is not zero (it does not exhibit the Meissner effect, for example).
 

Offline Atomic-S

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Some ideas for measuring wavelengths of laser beam:  If the beam burns up a diffraction grating, reduce its intensity by placing a transparent object in it such as a plate of glass, at about 45 degree angle, which will send part of it off in a different direction at lower intensity for measurement.  If it is still too intense, use an additional plate of glass in the reduced beam to make an even weaker version of the beam.  Or, if the beam is strong enough that it can be observed directly from atmospheric scattering, take the readings by looking at the beam at right angles to its direction of propagation; however be aware that this method may measure different phenomena than measuring the direct beam, because it is relying on scattered energy that may have been modified by the atmosphere.  In fact, this difference can be valuable because it gives you another to do the spectroscopy, and comparing the results (scattered by air vs. direct) would help you understand what was happening within the beam. 

Another idea:  Carry out your experiments as you have described, then repeat them with a glass plate inserted between the source and the target. The glass plate, being an electrical insulator (under normal conditions) , could affect electrical phenomena that may be present in the atmosphere, in a way that would be revealing as to what is happening. 
 

Offline alysdexia

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1,5 -> 1.5 or 15 (Napoleonic delimiter doesn't correspond with diction.)
it's -> its
from several -> for several
purple -> violet (Purple is the hue of grapeskins, nonspectral.)

http://en.wikipedia.org/wiki/Electrolaser
http://en.wikipedia.org/wiki/Skin_effect

A plasma's conductivity is somewhat worse than a semiconductor.
 

Offline Atomic-S

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It would appear that the future is here already.
 

Offline Atomic-S

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If your beam is creating a plasma in the atmosphere, rendering it conductive, that would automatically be a way that it could be rendered sensitive to your low-frequency coil. This sensitivity may somehow be modulating the effect of the high-frequency current.
 

Offline alysdexia

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